1. Field of the Invention
The present invention relates generally to a method and device for controlling the irrigation of plants in lawn care and in larger scale agricultural operations. The present invention relates more specifically to an improved irrigation control system that utilizes historical rainfall information and/or predictive rainfall information and/or restrictive watering information in determining an optimal irrigation plan.
2. Description of the Prior Art
Many systems have been developed to automatically control the distribution of water through irrigation means for both agricultural operations on a large scale and for individual domestic lawns on a small scale. These systems vary from exceedingly complex operations that incorporate soil moisture content sensors and field temperature measurements, to simple systems that operate strictly on a timed control basis. The effort in each of the past designs for such automated irrigation systems has been to minimize the need for human intervention in determining and effecting an optimal watering plan, such that labor costs are minimized and water usage efficiency is maximized.
Most irrigation control systems begin with basic timer circuitry that is capable of controlling one or a number of valves associated with water distribution conduits. In a typical domestic lawn watering system, a timer initiates a predetermined period of watering through the control of a valve connecting a water supply to a field of irrigation pipes and sprinkler heads. The typical timer system allows the user to set both the duration of the watering period and the frequency of the watering. A typical system may, for example, allow the user to water a lawn for a period of 45 minutes every Monday, Wednesday, and Friday during a week. Such timing systems can be combinations of mechanical and electrical devices that allow the user to simply switch days of the week in and out of the watering cycle and to switch the duration of the watering cycle in 5, 10, or 15 minute increments. Such systems might also be entirely electronic and may be capable of selecting a wide variety of watering plans from regular to completely random irrigation control.
It is also well known in the art to associate a watering or irrigation control system with a number of discrete irrigating pipe zones or fields. Whether by mechanical or electronic means, timing systems have been developed that switch various irrigation zones or fields on and off at regular intervals or in preplanned combinations. In this manner, watering control systems that may be of a relatively simple structure can be utilized to control and regulate the watering of domestic lawns or large scale agricultural operations in a manner that makes relatively efficient use of the water resources while minimizing labor costs associated with the manual operation of irrigation systems based upon human control.
Some irrigation and lawn watering systems have incorporated additional factors beyond preset time values, into the establishment of an irrigation plan. These external factors that figure into a determination of an irrigation plan have included rainfall measurements, soil moisture content measurements, temperature measurements, and other indications of the then existent need of the lawn or field for additional water. Some such systems have incorporated a simplified means for determining and acknowledging a historical rainfall amount, typically for a previous 24 hour period and the use of this information in "vetoing" the next watering cycle timed in the irrigation plan.
In its most simple form, lawn watering systems that incorporate rain stats can bypass a timed watering cycle when the water present in a rain stat is of a sufficient level. Such systems are typically limited to an acknowledgement of rainfall within the previous 24 hour period because of the necessity of resetting the system for subsequent rainfall measurements and the general assumption that any rainfall in earlier 24 hour periods of time would be of minimal relevance to the immediate water needs of the lawn or agricultural operation. Such rain stat operated systems have the drawback that differences in evaporation rates can significantly vary the appropriate impact that a given rainfall should have on a determination of additional irrigation quantities. In other words, a given quantity of rainfall at one time period during a day or at one time period during a particular season of the year, might result in water saturation for the plant life of a level sufficient that more than one cycle of the irrigation plan could be eliminated. On the other hand, evaporation rates during the afternoon in the summer time could be significant enough that no interruption of the standard watering cycle would be appropriate.
In order to overcome some of the drawbacks of these simple rain stat control systems, a number of improved irrigation control systems have incorporated soil moisture sensors in order to more accurately determine when additional irrigation is required. Such systems are typified by U.S. Pat. No. 4,396,149, issued to Hersch entitled "Irrigation Control System" as well as the companion U.S. Pat. No. 4,567,563 also entitled "Irrigation Control System". More complex systems that incorporate additional factors beyond simple soil moisture content include U.S. Pat. No. 4,755,942 issued to Gardner et al. entitled "System for Indicating Water Stress in Crops Which Inhibits Data Collection if Solar Insolation Exceeds a Range from an Initial Measured Value" and further in Reissue Patent No. 31,023, reissued on Sep. 7, 1982, to Hall entitled "Highly Automated Agricultural Production System". In these more complex patents, the systems described utilize not only soil moisture content, but canopy temperatures and soil temperatures for a more accurate determination of the water needs of the plant life being monitored.
Despite all of the various systems that have been developed to monitor the water needs of lawns and agricultural operations, it is nonetheless common place to see automated irrigation systems in full operation during rainfall. The reason for this is that none of the existing systems, regardless of their ability to determine historical rainfall amounts and soil moisture content are capable of storing historical rainfall data, of anticipating that rain will occur during an automated irrigation cycle, or of receiving a remote signal indicative of predictive rainfall data or restrictive watering data. There has heretofore not been disclosed in the prior art a means for bypassing or otherwise controlling an automatic irrigation system by storing and processing historical rainfall data, predictive rainfall data or restrictive watering data so as to appropriately preclude the implementation of that irrigation cycle. It would be desirable, therefore, to have a system capable of acknowledging historical rainfall data without the drawbacks of the prior art systems and utilizing such data to assist in the control and operation of an irrigation plan. It would be desirable to also use predictive rainfall data to create and execute an irrigation watering plan. It would be additionally desirable to have a system capable of utilizing historical rainfall data or a system with remote signaling which uses predictive rainfall data or restrictive watering data to control and operate an irrigation plan.